臺灣大學: 應用力學研究所郭茂坤江崇煜Jiang, Chong-YuChong-YuJiang2013-03-212018-06-292013-03-212018-06-292011http://ntur.lib.ntu.edu.tw//handle/246246/249857本研究利用Mie理論及並矢格林函數，分別分析球型金屬(金、銀)奈米粒子或奈米殼(nanoshell)受到平面波及電偶極波源在不同波長激發下，所表現的各種模態，例如偶極模態、四極模態、六極模態。對於平面波激發，分析奈米粒子的吸收截面積與散射截面積行為。對於電偶極激發，則分析受到奈米粒子或奈米殼的影響下之近場及遠場行為，例如輻射功率與非輻射功率。為進一步探討這些模態對兩個螢光體(予體、受體)之間的Förster共振能量轉移(Förster resonance energy transfer; FRET)之影響，本研究以雙電偶極(bi-dipole)波源模擬之，依據雙電偶極的方向，分成同向(反對稱)及反向(對稱)兩種波源。 數值模擬結果顯示，同向(反對稱)的雙電偶極可以激發出奇數項的模態(偶極模態、六極模態)；而反向(對稱)的雙電偶極，則可激發出偶數項的模態(四極模態、八極模態)，這些模態與平面波激發的結果一致。金奈米粒子及金奈米殼僅有偶極與四極模態表現，其他高階模態因波長較短，易被金吸收故不表現，另外在510-540 nm之間有極強的材料吸收。銀奈米殼則有各個模態的表現，且不同階模態的波長會隨內徑對殼層厚度的比值增大而增長，另外在330-355 nm之間有極強的材料吸收。其中四極模態的波寬較窄，且其近場及遠場行為皆優於其他模態，可被利用形成一個小型共振腔，幫助兩個位於南北極的螢光體(予體、受體) 之Förster共振能量轉移，適合實現奈米雷射的構想。 最後分析不同比例的金銀合金奈米殼，結果顯示其模態(偶極、四極模態)依據合金比例介於金、銀奈米殼的模態之間。The plasmonic modes of Au and Ag nanoparticles (NPs) and nanoshells (NSs) excited by plane waves and electric dipoles are studied by using Mie theory and dyadic Green’s functions; e.g. the dipole, quadrupole and sextupole modes. For the plane wave excitation, the absorption and scattering cross sections are analyzed. For the dipole excitation, the near-field and far-field responses (e.g. radiative and nonradiative powers) are analyzed. Furthermore, to study the enhanced FRET between a donor and acceptor by these modes, two types (symmetric and anti-symmetric) of bi-dipole are used for simulation. Numerical results show that anti-symmetric bi-dipole can excite the dipole and sextupole modes, and the symmetric one the quadrupole and octupole modes. These modes are in agreement with those excited by a plane wave. For Au NP and NS, only the dipole and quadrupole modes are observed, while the other higher-order modes are not. In addition, there is a strong absorption band at 510-540 nm. For the Ag NS, the dipole, quadrupole, sextupole, and octupole modes are observed. Moreover, these modes are red-shifted as the ratio of the core radius to the shell thickness increases. In addition, the strong absorption band is at 330-355 nm. The quadrupole mode exhibits its superiority in the near and far fields. Therefore it can be utilized to form a resonant cavity for enhancing the FRET of a donor and acceptor. This is to say the quadrupole mode of Ag NS can be used to realize the spaser-based nanolaser. Finally, the plasmonic modes of Ag/Au alloy NS are studied. These modes are in between those of Ag NS and Au NS, depending on the ratio of alloy.10454548 bytesapplication/pdfen-US奈米殼並矢格林函數吸收截面積散射截面積輻射功率非輻射功率對稱雙電偶極反對稱雙電偶極Forster共振能量轉移偶極模態四極模態。nanoshelldyadic Green’s functionsabsorption cross sectionscattering cross sectionradiative powernonradiative powersymmetrical bi-dipoleanti-symmetrical bi-dipoledipole modequadrupole modeForster resonance energy transfer (FRET).thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/249857/1/ntu-100-R98543047-1.pdf